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      <title>5、线程池 - 交互式测验</title>
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      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>5、线程池 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
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          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "当一个新任务提交给ThreadPoolExecutor时，如果当前运行的线程数已达到corePoolSize，并且工作队列（workQueue）也已满，但运行线程数仍小于maximumPoolSize，线程池会如何处理这个任务？",
    "options": [
      "将任务放入工作队列的末尾，等待核心线程空闲。",
      "立即根据拒绝策略（handler）拒绝该任务。",
      "创建并启动一个新的非核心线程来执行该任务。",
      "抛出IllegalStateException，因为核心线程和队列都满了。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "根据线程池的任务调度逻辑，当核心线程池已满时，会尝试将任务放入队列。如果队列也满了，线程池会检查当前线程数是否达到了maximumPoolSize。如果没有达到，它会创建新的“临时”或“非核心”线程来处理这个任务，以应对突发的高负载情况。",
    "source": "文档中「线程池的任务调度」部分",
    "hint": "文档中描述了任务提交的完整流程，思考当核心池和队列都无法接收任务时，线程池的下一步扩展行为是什么？"
  },
  {
    "question": "在处理I/O密集型任务（如数据库访问、网络请求）时，为什么文档推荐将线程池的核心线程数设置为大于CPU核心数的数量（例如CPU核心数*2）？",
    "options": [
      "为了减少线程上下文切换带来的开销。",
      "因为I/O密集型任务需要大量的计算，更多的线程可以并行计算。",
      "因为线程在等待I/O操作时CPU是空闲的，更多的线程可以利用这些空闲时间去处理其他任务。",
      "为了强制所有I/O操作串行执行，保证数据一致性。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "I/O密集型任务的特点是线程会花费大量时间等待I/O操作（如读写数据）完成，在此期间CPU是空闲的。设置更多的线程，可以使得CPU在一个线程等待I/O时，切换到另一个已经就绪的线程去执行任务，从而最大化CPU的利用率，提高整体吞吐量。",
    "source": "文档中「线程池核心数的设置」-「对于I/O密集型任务」部分",
    "hint": "思考当一个线程在等待网络响应时，CPU处于什么状态？如何才能不浪费CPU资源？"
  },
  {
    "question": "根据文档描述，`LinkedBlockingQueue`相较于`ArrayBlockingQueue`在高并发场景下的一个主要性能优势是什么？",
    "options": [
      "`LinkedBlockingQueue`是基于数组实现的，查找速度更快。",
      "`LinkedBlockingQueue`使用分离的锁（putLock和takeLock）进行入队和出队操作，提高了生产和消费的并行度。",
      "`LinkedBlockingQueue`必须在初始化时指定容量，能有效防止内存溢出。",
      "`LinkedBlockingQueue`在插入或删除元素时不会产生额外的对象实例，减少了GC压力。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档中明确指出，`LinkedBlockingQueue`为添加和移除操作使用了不同的锁（putLock和takeLock），而`ArrayBlockingQueue`使用同一个锁。这种锁分离的设计允许生产者线程和消费者线程在队列两端同时进行操作，从而大大提高了高并发环境下的队列吞吐量。",
    "source": "文档中「线程池工作队列」-「LinkedBlockingQueue和ArrayBlockingQueue区别」部分的第4点",
    "hint": "文档对比了两种队列的锁实现机制，这种机制的差异直接影响了并发性能。"
  },
  {
    "question": "当线程池和任务队列都达到饱和状态时，如果采用`CallerRunsPolicy`作为拒绝策略，会发生什么？",
    "options": [
      "线程池会抛出`RejectExecutionException`异常。",
      "新提交的任务会被直接丢弃，并且没有任何通知。",
      "队列中等待时间最长的任务会被丢弃，然后尝试接纳新任务。",
      "新提交的任务将由提交该任务的线程（调用execute方法的线程）自己来执行。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "`CallerRunsPolicy`是一种调节和反馈机制。当线程池无法处理新任务时，它不会抛弃任务或抛出异常，而是将任务的执行责任交还给任务的提交者。这会减慢提交者的速度，因为提交者必须自己完成任务后才能继续提交新的任务，从而形成一种自然的流量控制。",
    "source": "文档中「拒绝策略」部分",
    "hint": "这个策略的名字“Caller Runs”直接暗示了当任务被拒绝时，由谁来运行它。"
  },
  {
    "question": "在`ThreadPoolExecutor`的七个核心参数中，`keepAliveTime`参数的作用是什么？",
    "options": [
      "定义核心线程（core threads）在空闲时可以存活的最长时间。",
      "设置任务在工作队列中可以等待的最长时间。",
      "指定所有线程（包括核心和非核心）的固定生命周期。",
      "定义超过核心线程数的“临时线程”在空闲时，在被终止前可以存活的最长时间。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "`keepAliveTime`参数专门用于管理非核心线程的生命周期。当线程池中的线程数超过`corePoolSize`时，这些多出来的线程在完成任务后如果处于空闲状态，`keepAliveTime`就是它们等待新任务的超时时长。一旦超过这个时间，这些空闲的非核心线程就会被回收，从而在系统负载降低时自动缩减线程池大小。",
    "source": "文档中「线程池7大核心参数」部分",
    "hint": "这个参数与线程池的“收缩”能力有关，但它只影响特定类型的线程。"
  },
  {
    "question": "调用线程池的`shutdown()`方法后，线程池会进入什么状态？它会如何处理已提交的任务？",
    "options": [
      "进入`STOP`状态，立即中断所有正在执行的任务并清空任务队列。",
      "进入`SHUTDOWN`状态，不再接受新任务，但会继续处理完队列中所有已存在的任务。",
      "进入`TERMINATED`状态，所有线程被立即销毁，任务丢失。",
      "进入`RUNNING`状态，但内部标记为“关闭中”，新任务会被拒绝。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "调用`shutdown()`方法是一种平缓的关闭方式。线程池会转换到`SHUTDOWN`状态，这个状态的特点是：1. 拒绝所有新提交的任务。2. 允许线程池继续执行已经在工作队列中等待的任务以及正在执行的任务。直到所有任务都完成后，线程池才会进入`TIDYING`并最终`TERMINATED`。",
    "source": "文档中「线程池的运行状态」部分",
    "hint": "与`shutdownNow()`的“立刻”和“强制”相比，`shutdown()`是一种更“优雅”的关闭方式。"
  },
  {
    "question": "哪一种由`Executors`工厂类创建的常见线程池，其内部使用`SynchronousQueue`，并且线程数量几乎是无限的，特别适合执行大量、耗时短的异步任务？",
    "options": [
      "FixedThreadPool",
      "SingleThreadExecutor",
      "CachedThreadPool",
      "ScheduledThreadPool"
    ],
    "correctAnswerIndex": 2,
    "explanation": "`CachedThreadPool`的特点是`corePoolSize`为0，`maximumPoolSize`为`Integer.MAX_VALUE`，并使用`SynchronousQueue`。`SynchronousQueue`本身不存储元素，每个插入操作必须等待一个相应的删除操作。这意味着每当有新任务到来，如果没有空闲线程，线程池就会立即创建一个新线程来处理它，因此它能灵活地根据负载增减线程，适合处理突发性的、大量的短时任务。",
    "source": "文档中「常见的线程池」-「CachedThreadPool （无限线程数的线程池）」部分",
    "hint": "思考哪种队列“没有容量”，迫使线程池为每个新任务寻找或创建一个执行者。"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
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        const optionsListEl = document.getElementById('options-list');
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        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

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          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
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          updateNavigationButtons();
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        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
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            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
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            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
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                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
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                    child.style.borderColor = '#f5c6cb';
                }
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        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
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                loadQuestion();
            }
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        function showHint() {
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                hintContainerEl.textContent = currentQuestion.hint;
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            } else {
                hintContainerEl.style.display = 'none';
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        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  